Metallurgical process



`Aug. 9, 1932- J. ALLINGHAM METALLURGICAL PROCESS Filed April 17, 1951 Inventor; cfozrz AZZzlngiwwM er ta-vraag.

Patented Aug. .9, 1932 raaf :roniv ALLINGHAM, or Los ANGELES, ciinironiviiiA METALLURGICAL racer-:ss

Application lerd April 17,

i In this specification, and the accompanying drawing, I shall describe and show a preferred manner yof utilizing my invention,

' andspeciiically mention certain of its more important objects. I do not limit Ymyselito the particular methods disclosed, however, since'varous changes and adaptations may be made therein without departing from the essence of my Vinvention as hereinafter claimed; and-objects and advantages, other than those specifically mentioned, are included within the scope of the invention.

My invention relates to means for extracting certain metals from ores and mill tailings; and particularly to processes for the extraction of' mercury, gold,.silver, and copper from tailingsvwhich have resulted from theV Patio and Pan-amalgamation processes.

' Tailings of the latter class frequently contain organic matter in chemical combination with the above stated metals, forming organic salts thereof. Hitherto it has been. found to be impracticable to recover these metals from such organic salts, by any method known to the art.` Cyanide and hypo processes in such cases are of no commercial value, chiefly on account of the insolubility of the organic salts of the particular 4metals we are here considering. l

The principal object of my invention is to provide practical commercial means for recovering mercury, gold, silver," and copper, from tailings and ores of the character described; and among the subsidiary objects are to provide a simple arrangement of 193i. sei-iai No. 530,830.

ores, even when such metals are in the forml ot organic salts.` A

The chemistry involved in treating'such ores and tailings as those mentioned above,

is often'very complex, on account of changes which have been eiiected by decomposing' organic matter extending over long periods of time. Such decomposing organic matter is commonly known as humus. The acids from thishumus are commonly called humic and ulmic acids, and their salts react upon metals to produce humates and ulmates. *Ink reality this humus consists of many complex organic compounds and acids. MyV experimental work in this iield hasV demonstrated that the metals in such ores and tailings, although they may iirst exist in the form of chlorides, carbonates, sulphates, and! even` metallic gold, are changed after long peri'- ods of time to the form of complex organic salts 'when humus is present, especially when they are -exposedto the effects of thel atmosphere and weather. A I have lfound that certain of the inorganic vsalts of the particular metals mentioned, `are soluble in hypo (thiosulphate of calciumor sodium), or 4man alkaline solution of cyanide, but that most of the organic salts of these metals areinsoluble inhypo and cyanide. I havediscovered, however, that there v are several ways of converting suchinsoluble organic metallic salts into soluble salts.

One method of accomplishing this resulty consists in the process Voi oxidizing the organic metallic salts, and these free organic acids, in the-dump.v Making the material slightly alkaline renders` it more easily oxidizable, and a slight excess of *alkali* may play' the role `of a catalytic agent. Such material originally is slightly acid, diie tothe free organic acids present. When lime is added it combines with these free acids to form or- Y ganic calcium salts. This treatment ordinar-` ily will not'make theroxidation complete however, and complete oxidation can only be obtained in this manner byrepeatedly wetting and drying the treated material.

A second' method is to. treat the materia described, ina wet condition, with sulphur dioxide, or directly with. sulphurous acid.

ion

The effect of this treatment is to break up the organic salts of the metals, thus producing sulphites of the metals, and liberating non-metallic organic salts.

A third procedure comprises a combination of the above two methods, and it will in'most cases be found to be the most economical and satisfactory process for obtaining the highest recoveries of metals from material of the character described. In this combination treatment, the addition of an Valkaline thiovsulphate changes the insoluble sulphitesto the form of soluble double thiosulphates of Y the metals.

Passing now to a description of the process,

and the arrangement of'apparatus that constitutes thepresent invention, the first step is to prepare a suitable pulp of the metalbearing material that isvto be treated.` Tf such lmaterial is not already sufficiently fine,

it should be ground to a fineness adapted to Vgive the best recovery in the process. If it is fine enough to pass a 10D-mesh screen, it ordinarily will be well adapted for the process to be described.' The fine material is mixed with Water in suitable proportions, in pulp- Y ing'tank 1. The ratio of the material that is to be treated to water, may be one to two, o r other suitable proportion, determined by the character ofthe material. The pulp passes from pulping tank 1 into one or more ox-idation'tanks 2 connected in series, but beffore entering thel first of these'two tanks, lime is added at 3, in sufficient quantity to make the pulp slightly alkaline.

The second step in the'process consists inl` thoroughly oxidizing the alkaline pulp in tanks 2. This may be accomplished in several well known ways, suchas by passing air through thepulp in these tanks,'or by spraying the pulp into the atmosphere withinthe tanks.

The third step of the Aprocess consists in subjecting 'the oxidized pulp coming from v tanks 2,` to the action of sulphur dioxide gas. Such gas may be prepared in any suitable inanner, as by means of a pyrite roasterz/l.

Theoxidized pulp fromtanks 2 flows-'into an SO2 absorber 5, this being suppliedwith sulphur dioxide ygas from the pyrite roaster.

A convenient form of the absorber 5 is what' iscominonly knownas a disk absorber.-;

This comprises a horizontal cylindrical 'tank having a series of Idiscs-therein `uponine chanically driven shaft, thev discs being foraminousin character, thus presenting a large amount of surface that is constantly kept Wet" by the revolution of the discsr The'amount of sulphur dioxide -gas that is necessary in.

ordinary practice has been Vfound to be from 5 to 15 pounds per ton of thematerial treated,

but the exact amount required Vwill depend upon the charac-ter of the material, and should be determined by experimental runs. The fourth step in theprocess isy to pass treated tank'7.

the pulp which has been oxidized and subj ected to the action of the sulphur dioxide gas, into one or more treatment tanks 6 in series. Tn these tanks the pulp is treated to the action of an alkaline thiosulphate, such as calcium thiosul'phate. The amount of this reagent varies in practice with the character of the tailings, but ordinarily about eight pounds of the reagent per ton oftailings, is sufficient to obtain `commercial extractions. The y thus pulp then passes to filter storage from a storage tank 9. The barren solution,`

invthis tank comes from other apparatus tobe described presently. The non-metallic solid material produced by filter 8 is discharged tofthe dump-at 10. rV The filtered soo-j lution of metallic salts fromlthis filter is Vpassed through several'clariers 11 in series,

to permit of settlement lof suchnon-metallic v solid particles as may stillbe held in suspension. Y

From-tlielast tank 11 of Vtherabove series, the metal bearing solution ,passes to one or lmore precipitation tanks v12 infseri'es, as the sixthstep' of the process. On its Way to these tanks, a suitable precipitating agent, such as ground ironrsponge, is addedl at the point 13, for causing'precipitation of the metallic salts contained in the solution. c

The seventh step consists in separating the precipitated metallic salts' from the barren liquid, by methods of filtration. Fromthe `precipitation taiiks12 the material flows to a cone tank 14, where'the heavier lportions of the precipitate settles. l The'solution, coutaining some' of the lighter portions Iof the precipitate in suspension, then flows to ai filter 15, and the filtered barren solution from` the latter is pumped to barren-solution tank.

Q'mentioned above.4 The precipitates from conewtank lll, and also `from filter `l5v .are

pumped into one or more precipitate presses 16, where most of the vremaining liquid isy squeezed out of the precipitates. i

The eighth and final step of the process consists in passing the wet pressed precipitate, produced bypresses 16, into a mercury retort Yfurnace 17, where mercuryisdi'stilled from the other metallic materiah The mercuryvaporl is led to condenser 18, wheremetallic mercury is collected.

, The metallic material that remains in retort 17, after completing the distillation process, is a concentrate of copper, silver, and gold. This may be smelted by usual methods.

' Tank 19 is a return pulp tank for receiving excess pulp from the `large filter 8 at eachA cycle of its operation. It discharges into the lilter storage tank.V

It is desirable to supply mechanical agitation means in tanks 1, 2, 6, 7,12 and 19, as by power driven paddles 20. It Will be understood that various valves, pumps', miscellaneous appliances, and sources of mechanical power, Will be provided Where required, to accomplish the' desired processes in a convenient and economical manner.

It Will be noted that, except for the necessarily Vcyclic operation of the filters and presses, my process is substantially continuous in character. It Will-be seen further that it is Well adapted for treating ores and tailings of the kind described, that :contain organic metallic salts of gold, silver, copper, or mercury, in an eiicient and economical manner; and it Will therefore be recognized as constituting a` commercially practical process. Y

Having thus fully described my invention, I claim: f

1. The metallurgical-process for treating material containing organic salts of gold, silver, copper, or mercury, Which comprises; making said Amaterial slightly alkaline, to render the salts more easily oxidizable; oxidizing the salts in the alkalized material; and then subjecting theoxidized salts to the action of sulphur dioxide.

2. The metallurgical process for treating material containing organic salts of gold, silver, copper, or mercury, Which comprises;

silver, copper, or mercury, which comprises;

making said material slightlyalkaline; oxidizing said salts in the alkalized material;

treating said oxidized salts vto convert them 7 into metallic sulphites; converting said sul-y phites into soluble salts in solution; and then adding liron sponge to said solution to precipitate the metals therein. j

6. The metallurgicalrprocess for treating material containing organic salts of gold, silver, copper, or mercuryfvvhich comprises; in sequence; preparing a pulp of said material; oxidizing said'pulp in the presence of an alkali; treating the oxidized pulp ina manner to change the metallic salts to metallic sulphites; treating the thus prepared material ina manner to change saidsulphites to soluble double thiosulphates of the metals, in solution; separating vthe solids from said solution; and Vprecipitating the metals from said solution.

JOHN ALLINGHAM;

making Vsaid material slightly alkaline, to-

render the salts more easily oxidizable; oxidizing the salts in the alkalized material; subjecting the oxidized salts to the action of sulphur dioxide; and then dissolving the thus prepared salts in a thiosulphate solution.

3. The metallurgical processY for treating material containing organic salts ont gold, silver, copper, or mercury, Which comprises; making said material sli htly alkaline, to render said salts more easiy oxidizable; oxi! dizing said saltsrin the alkalized material; subjecting said oxidized salts in a Wet condition, to the action of sulphur dioxide; and then subjecting the thus prepared metallic sulphites to the action of an alkaline thiosulphate, to change them to the form of soluble double thiosulphates of the metals.

4:. The metallurgical process for treating material containing organic salts'of gold, silver, copper, or mercury, Which comprises; making said material slightly alkaline; oxi-V dizing said salts in the alkalized material; treating said oxidized salts to convert them lll) 

